STRUCTURE AND COMPOSITION OF SWEET SORGHUM STALK COMPONENTS

Stem bark and pith of sweet sorghum were analyzed with reference to th eir sucrose, simple reducing sugars, cellulose, hemicelluloses, lignin and associated phenolic acids contents. Moreover, lignin monomeric un its (guaiacyl and syringyl) engaged in non-condensed structures were c haracterized by thioacidolysis, whereas cell wall associated phenolic acids (p-coumaric and ferulic acids) were estimated by alkaline hydrol ysis at 170 degrees C. The results obtained showed that bark and pith are heterogeneous as far as their chemical composition and the structu re of their-chemical components are concerned. In particular, the pith content in water soluble sugars is twice as high compared with the on e in the bark, whereas bark is enriched in lignocellulosic fibres. Bar k lignin is twice as important in content and less condensed in struct ure compared to pith lignin. p-Coumaric acid is the predominant p-hydr oxycinnamic acid associated to the cell walls, whereas ferulic acid is present in significant quantities. (C) 1997 Elsevier Science B.V.